Light-sensitive medium and process of producing the same



Patented Feb. 23, 1926.

UNITED STATES'YPATENT OFFICE.

MURRAY C. BEEBE, OF CINCINNATI, OHIO, ASSIGNQR TO THE WADSWORTH WATCH CASE COMPANY, OF DAYTON, KENTUCK Y,.A CORPORATION OF KENTUCKY.

LIGHT-SENSITIVE MEDIUM AND PROCESS OF PRODUCING THE SAME.

No Drawing.

To all whom, it may concern:

Be it known that I, MURRAY C. BEEBE, a citizen of the United States, residing at Cincinnati, in the county of Hamilton and State of Ohio, have invented certain new and useful Improvements in Light-Sensitive Mediums and Processes of Producing the Same, of which the following is'a specification.

The invention relates to a light-sensitive medium for use in the optical reproduction of designs, characters, images of objects, etc, and to a method of producing such a composition.

The primary object of. the invention is to provide a varnish-like medium which is well adaptedfor use in the industrial arts in the optical reproduction of characters, designs,-

pictures, images, etc. The improved lightsensitive medium may be usefully employed, for example, in producing a resist for etching purposes. It is possible, with the improved light-sensitive medium, to project a light image onto a coating applied to a metal surface, or other surface and in this v manner under the action of light, and a suitable accelerator which is adapted to rapidly accelerate the change which occurs in the medium under the action of light. The improved medium does not depend on the usual type of sensitizers, such as silver salts, an'iinoniuin bichromate, potassium bichromate, etc.

The invention finds a very useful application to the optical production of replicas on metal, films, glass, etc. It marks a radical departure from existing photographic practice in that materials are used which hitherto have not been considered available for the Application filed March 8, 1922. Serial No. 542,124.

516,865, filed November 21, 1921, and is also in the nature ofacontinuation in part of my application Number 488,605, filed July 30, 1 921. In the earlier filed application, it was pointed out that special li ht-sensitive coatings were to be made the su ject matter of a separate application for patent; and in application Number 516,865, there is described and claimed a process of utilizing coatings of this character, said process being preferably practiced by the use of the improved light-sensitive varnish described and claimed herein.

The light-sensitive varnish-like medium described and claimed herein is affected selectively by the action of light when the light is transmitted through a transparency embodying any desired design, character, or image of an object. However, it is evident that some action other than an ordinary drying action which is attributable to the character of the varnish employed occurs. Thus, a light sensitive oil, such as tung oil, especially when there is incorporated therewith a suitable accelerator, will, under exposures I which are very much shorter than is required for an ordinary drying procedure, produce a latent image in a coating of the varnish. If a film of the improved varnish, after exposure to light projection, be allowed to dry in the air for a few hours, the parts of the coating which were not acted upon by the light during exposure become less soluble than those parts which were most strongly illuminated during the projecting operation, thus demonstrating that a latent image was formed in the coating during the action of the light image upon the coating.

As an example of a varnish made in accordance with the invention, the following is given Incorporate in 100- gms. of'any suitable resinous or gum varnish 3 gins. of iodine, as an accelerator. Such a varnish preferably is formed with tung oil present as a large constituent, and'also preferably has incorporated therewith various metal salts, oxides, or the like, which are known in the varnish art to be useful as dri'ers. The varnish may, if desired, be of the composition. given as anexample in my above-mentioned application Number 516,865, of which the present application forms a continuation in part. Thus, the composition may be as follows:

- Grams.

Copal 10 Tung oil 25 Lead resinate 5 Turpentine 15 The copal and tung oil may be cooked together to dissolve the copal and bring the solution to a desired consistency, in accord ance with the general method commonly employed by varnish makers. nate and turpentine may then be admixed with the solution.

The tung oil present in a varnish prepared as stated is light-sensitive, and a coating of such a varnish may have formed thereina hardened or set image by'acting on the coating selectively with light transmitted through a design or through an image of an object, after which the coating may be developed in any desired manner. It is preferred, however, to incorporate in the varnish suitable accelerating agents, such as those mentioned in said application 516,865. Thus, suitable ingredients which may serve as accelerators to hasten the drying action are: iodine, metallic oxides, such as ferric oxide, manganese dioxide, lead oxide, barium carbonate, Zinc oxide, etc.; also, the resinates and their organic combinations may be used in the varnish as drying agents, or as accelerators. These substances may be used in any desired combination, or any one or more of these ingredients may be selected and used, as desired. Equivalent substances may be used as accelerators.

Some of the ingredients mentioned are slower in their action than others. For instance, copper, barium, and iron in the form of metallic resinates, if used alone, do not operate to transfer oxygen to the oil as rapidly as may be desired. Where they are used, it is preferred to employ also lead oxide, manganese oxide, lead resinate, or manganese resinate, or any desired number or combination of these ingredients. Any metal salt or compound of analogous action may be employed. The higher the proportion of leader manganese oxide or salt, the faster the drying action. Ordinarily, however, the special accelerators employed, as

distinguished from tung oil, for example, which is quite light-sensitive, are employed in relatively small proportions, as indicated in the example given above.

It should be added that when a suitable metallic salt, such as lead resinate or lead oxide is employed in connection with a suitable amount of lodme, for example, there is "formed in the varnish a metallic halide i which is dispersed throiwhout the varnish.

That is, these substances form, for example,

The lead resipension in the varnish. Such a metallic halide is readily decomposed under the action of the light projected upon or transmitted to the coating in producing an image in the coating; and, while it is not desired to limit the invention by any theory which may be advanced, it may be said that the liberated iodine doubtless acts as a catalyst in the change which takes place in the portions of the varnish coating which are affected by the action of the light projected thereon or transmitted thereto.

T ung oil and linseed oils are examples of the drying oils, but tung oil is more lightsensitive than linseed oil and hence its use is especially desirable where a very rapid change to the insoluble condition under the action of light is of prime importance. The

drying oils are hydrophobic colloids and contain fatty acids which doubtless are active in the changes which occur in the varnish coating under the action of light. Such action is greatly expedited, moreover, when a metallic halide, or a suitable halogen-liberating agent is dispersed in the varnish. Thus, a metallic'halide incorporated in the varnish serves as a halogen-liberating colloid.

It is to be understood that the varnish described above is only an example of varnishes which may be used in the process, and that any equivalent varnish may be used without departure from the invention.

As will be understood from the description thus far given, the photo-sensitivity 0 oils, orof substances having characteristics similar to tung oil (Chinawood oil) is greatly increased, or the transformation thereof under the action of light into a more insoluble condition, is greatly expedited by the use of' special sensitizing ingredients, or accelerators, such as ferric oxide, lead resinate, lead iodide, etc.

The varnish may be applied to any desired surface in any practical manner. It may be, for example, flowed or spread upon a metal surface to form a thin coating thereon. The light-sensitive ,coating may then be exposed to the selective action of light, as by projecting light from any suitable source through a transparency embodying or hearing a character, design, or image of an object, until the coating feels dry or only partly tacky to the touch. The time required will vary from a few minutes in less sensitive coatings to a few seconds for more sensitive coatings. The selective action of the light upon the coating may be secured by transmitting the light through a suitable negative overlying the coatin After exposure, the print is developed in any suitable way. It may, for example, be

dipped in a solution of oil red and carbon tetrachloride for about one-fourth of a second, and may then be washed in benzme velopment, the print will be a transparent red positive, if a negative image has been used. Any other suitable method of developing the image may be employed. For example, the soluble portions of the coating may be washed off in any suitable manner. Also, the hardened or .set image may be colored, or stained in any suitable manner.

After the development operation, the surface exposed or left unprotected by re moval of the soluble portions of the coating may be etchedby means of acid or other suitable etching agents, in accordance with known methods.

Contrary to well knownv phenomenon in printing on gelatine coatings by means of light, the first action which oceurs'with the improved coating under the action of light appears to be at the point of contact between the coating and its support, and the trarisformation of the coating gradually works forward to a variable extent, depending upon the variability of the light action upon the coating. Thus, a continuous-tone image projected on the coating will, on de velopment form its front face, produce a variable thickness result, in -'marked contrast to carbon printing which must be developed from the back.

It may be stated that oil red, oil blue,

=' oil yellow, etc., are terms applied to dye stuffs, or dyes, which are insoluble in water, but are soluble in oil. Such dyes are used to make an image visible during development.

The exact chemical reactions which take place in the formation of a photographic image in a coating are unknown. However, where tung oil is present as a constituent of the varnish, it is probable that woleostearic acid, a constituent of tung and other light-sensitive oils, is, under the action of light, converted into ,B-oleostearic acid. These acids and analoguous substances play a cooperating or dominant roll. Similarly, the fatty acids of other oils, when present in varnish, will, under the action of light, be affected in such manner as to causev the varnish coating to undergo .a variable change in solubility.

The unique property of light-sensitive oils has an important bearing in the industries, especially in the graphic arts, etc,

for the production of photoengravings and all uses in whicha strong chemical-resisting coating is required; also in the production of transparent films for one purpose or another, either without color, in one color, or stained in different colors, whether the image to be reproduced is optically projected onto the coating, or is printed through a negative. A hitherto unoccupied field is open through this invention which makes thoroughly practicable the direct projection of a photographic image onto metal, as in half-toning, line etching, etc., directly from an adequately illuminated drawing or transparency. The'coating may, however, be applied to any desired surface, and the image formed in the coating may be utilized as desired. 1

The results produced through the use of compositions containing photo-sensitive oils, or their equivalents, with a suitable accelerator, are, among other things, clear, transparent films, if desired, which are elastic, water-proof, non-conducting and highly resistantto chemical solutions and acids, and hence very durable.

Print-s produced. by the use of the new medium, whether in one form or another, may be stained in various colors, or may be rendered opaque in their deepest shades by the addition of a pigment to the coating.

The use of a halogen-liberating agent, for example, a metallic halide, in a suitable medium of. varnish-like consistency is deemed highly important, especially where very rapid transformation of the coating is desirable. Any suitable medium or vehicle containing as a large constituent thereof a body which is capable of being transformed, polymerized, hardened, or set under the action of light, with such action expedited by the use of the halogen liberated may be employed. This characteristic is present in a very high degree in tung oil, but is not limited thereto. I

Because, of the pioneercharacter of the invention, great latitude is claimed in forming the composition, the developing and staining steps, method of applying the coating, degree of acceleratio-n,.and the application of the image to the coated surface, because these and any related factors, are of necessity modifiable according to the exigen cies which inevitably arise in utilizing an invention which isadaptable to so many varied purposes.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the priorart.

What I regard as new, and desire to secure by Letters Patent, is

1. For use in processes of the character set forth, a varnish comprising a suitable base,

a light-sensitive. oil in relatively lar e amount, and an accelerator in relatively small amount, said accelerator serving to accelerate the selective action of light upon said varnish under photographic action.

3. For use in photogra hic processes, a varnish comprising a suitable base, tung oil in relatively large proportion, and an accelerator serving to accelerate the selective action of light upon said varnish under photographic action.

4. For use in photographic processes, a varnish which comprises as a large constituent thereof a light-sensitive oil containing a fatty acid, and an accelerator comprising a halogen-liberating agent.

5. For use in photographic processes, a varnish comprising a body having constituents adapted to be hardened under the action of a halogen, and an accelerator comprising a halogendiberating agent.

6. For use in photographic processes, a varnish comprising a body adapted to change to a more insoluble condition under the action of a halogen, and a metallic halide adapted to. liberate halogen under the influence oflight. 7. For use in photographic processes, a varnish comprisin as a large constituent 'hydrophobic COllOldS, and a colloidal accelerator comprising a halogen-liberating agent. 4 V V g 8. For use in photographic processes, a varnish comprising a lightrsensitive oil, a natural (Kying agent, and a. halogen-liberating agen 9. For use in a photographic processes, a varnish comprising an oil containing a fatty acid, and an iodide.

10. For use in photographic processes, a

varnish comprising a resin base, a light sensitive oil used in larger amount than said base, and a relatively small amount of accelerating agent dispersed -in colloidal form in the varnish and serving to accelerate the selective action of light upon said varnish under photographic action.

11. For use in photographic processes, a varnish comprising a light-sensitive oil combined with agents rendering the varnish susceptible to a selective change in its solubility when the varnish is employed as a coating and subjected to the selective action of light in accordance with an image.

12. A print produced by photographic process, said print comprising an image formed under the'selective action of light in a medium comprising an oil containing a I fatty acid.

13. A print produced by photographic process, comprising an image formed under 7 the seletcive action of. light in amedium comprising tung oil.,

14. A print produced by photographic process, comprising an image of insoluble character formed under the selective action of light in a medium comprising an oil containing a fatty acid and a halogen-liberating compound.

15. A print produced by photographic process, comprising an'image of insoluble character formed under the selective action. of light in a medium comprisng a halogenliberating agent and a body containing an oil having constituents adapted to be hardened by halogen liberated by said agent under such selective action of light.

16. A print formed by photographic process, comprising an image which comprises B-oleostearic acid formed under the action of light in a medium comprising aoleosteario acid.

17. The-process of forming a light-sensitive medium which comprises incorporating a halogen-liberating agent in a body comprising constituents capable of being.

transformed into insoluble condition by halogen liberated by said agent under the action of light.

18. The process of forming a light-sensitive medium which comprises incorporating a metallic halide as an accelerator in a body which comprises constituents adapted to be transformed into insoluble condition under the action of halogen liberated by the action of light.

19. The method of forming a varnish suitable for recording images which comprises incorporating a halogen-liberating agent in a medium comprising a light-sensztive oil.

20. The method of forming a varnish suitable for recording images which comprises incorporating a halogen-liberating agent in a medium comprising a resin and a 1ight-sensitive oil.

21. The method of forming a varnish suitable for photographic purposes which comprises incorporating a halogen-liberating agent in a resin base and a light-sensitive oil containing a fatty acid.

22. The method of forming a varnish suitable for photographic purposes which comagent in a medium which comprises a resin and a larger proportion of a hght-sensitive oil contain ng a fatty acid.

23. The method of forming a varnish suitable for photographic purposes which comprises incorporating a halogen-liberating agent and a natural drying agent in a medium comprising a light-sensitlve oil.

24. The method of forming a varnish suitable for photographic purposes which comprises incorporating a halogen-liberating agent and a natural drying agent in a medium compris ng a light-sensitive oil and a resin base.

25. The method of forming a varnish suitable for photographic purposes which comprises incorporating a halogen-liberating agent in a medium comprising tung oil.

26. The method of forming a varnish suitable for photographic purposes which comrises incomoratim a halo en-libcratin"' D C D agent in a medium comprising tung oil and a resin base.

27. The method of forming a varnish suitable for photographic purposes which comprises incorporating iodine and natural drying agents in relatwely small proportionin a medium comprising hydrophobic colloids in relatively large proportion which are capable of being transformed into insoluble condition selectively under the action of light. In testimony whereof I aflix my signature.

MURRAY C. BEEBE. 

